1. Field of the Invention
The present invention relates to a system for testing a plurality of control rod clusters positioned in a reactor vessel for any obstructions during insertion and withdrawal of the control rod clusters from a core of the reactor vessel and, more particularly, to a system for simultaneously testing all the plurality of control rod clusters.
2. Background of the Related Art
In nuclear power generation, a reactor vessel is located in a containment building and is the primary vessel wherein heat is generated for producing steam. The reactor vessel includes a flanged body having a flanged, removable upper head bolted atop its upper portion for forming a sealed enclosure. Fuel pellets, which are located within fuel assemblies, are positioned within the reactor vessel for producing a controlled nuclear fission which, in turn, generates the necessary heat. The containment building functions to contain any unlikely radiation leakage from the reactor vessel within the containment building.
To control the nuclear fission process, a plurality of control rods are either selectively inserted or withdrawn from the fuel assemblies. Control rods are typically stainless steel tubes encapsulating an absorber material, and are grouped together in a predetermined number, generally sixteen, forming a control rod cluster. There are typically sixteen control rod clusters in the reactor vessel. The control rod clusters extend into the fuel assemblies when fully inserted, and when the control rod clusters are withdrawn, they extend up and away from the fuel assemblies.
Each control rod cluster is attached to a control rod drive mechanism (CRDM) for axially moving the absorber material within the stainless steel tubes. An electromagnetic coil stack assembly is attached to the CRDM for electromagnetically supplying the CRDM the energy necessary to move the control rod clusters. A switchgear panel is connected to and supplies the electrical power to the coil stack assembly. A rod position indicator (RPI) is attached atop the electromagnetic coil stack assembly and, in cooperation with a RPI data cabinet electrically connected to the RPI, monitors the position of the control rod clusters. It is instructive to note that all of the above components, except the switchgear panel and the RPI data cabinet, are located within the containment building.
Due to safety regulations and the like, before starting-up the plant, each control rod cluster should be tested to ensure they may be inserted into and withdrawn from the fuel assemblies without hitting any obstructions. Present devices for testing the control rod clusters, as are well known in the art, insert them one cluster at a time. In such prior testing arrangements, an oscillograph is manually attached to the RPI data cabinet for receiving a digital signal and providing a trace test signal of the control rod cluster during testing. To start testing, test personnel energize the coil stack assemblies which fully withdraws the control rods, and then de-energize a predetermined coil stack assembly, such as by manipulating a switch in the switchgear panel, for fully inserting a control rod cluster. The oscillograph traces the fall of the preselected control rod cluster into the fuel assemblies on photosensitive paper for visual inspection by the test personnel to determine if any problem exists, as is well known in the art.
Although the present devices are satisfactory, they are not without drawbacks. The present device is time consuming because each control rod cluster is tested separately. In addition, if one wished to simulate an accident condition, all the control rod clusters should be inserted simultaneously. Such accident conditions may not be simulated by the present devices because the clusters may not be tested simultaneously. Further, some of the test personnel are required to be within the containment building during testing to operate the oscillograph, and this requires the test personnel to be temporarily exposed to radiation.
Therefore, a need exists for a system for simultaneously testing a plurality of control rod clusters: